This invention pertains to drainage culvert and in particular to surface drainage culvert of the type which accommodates sheet flow of surface drainage water like that commonly encountered on paved surfaces, such as highways and parking lots.
Drainage culvert of the general nature of the subject invention have been employed to intercept sheet flow drainage water for many years. Exemplary of the prior art is U.S. Pat. No. 3,714,786 which discloses a slotted drainage culvert comprised of a longitudinal grating which is lodged within a slot formed in a metal pipe. The grating is welded to the metal pipe, and includes a pair of upstanding bearing members which are separated by spacer means generally at the neutral axis of the pipe. Other forms of earlier prior art are also disclosed and discussed in this patent.
U.S. Pat. No. 3,714,786, while claiming to be an improvement over prior art drainage culvert, suffers deficiencies of its own. First, the disclosed grating, which is inserted within the slot in the pipe, must be specially fabricated to include the spacers which are welded serially along the length of the grating. Since such a grating is typically twenty feet in length and the spacers are placed at six inch intervals, a significant fabrication effort must be undertaken for each length of grating. Secondly, the grating is inserted within the slot and welded to the pipe periodically with fillet welds. If the welds are not strong enough or if a large load is placed directly upon the grate, it is possible that the grating can be separated from the pipe in use, necessitating its removal and replacement. There is no support for the grating other than the periodic fillet welds to the pipe. Another, and consequential, disadvantage of the drainage culvert of this patent is the cost. Since the grating must be individually fabricated, and then each grating fillet welded to the slotted culvert, a substantial amount of costly labor is required to fabricate each section of drainage culvert, or costly fabrication machinery must be employed.